Posted on by David Dickinson

How to Catch This Week’s ‘Ring of Fire’ Annular Eclipse

A perfect ring of fire captured by Kevin Baird on May 20th, 2012 from Bluit New Mexico. (Credit: Kevin Baird/Universe Today flickr Group).

The first solar eclipse of 2013 is upon us this week, with the May 10th annular eclipse crossing northern Australia and the Pacific.

2013 is an off year for eclipses. There are five eclipses this year, three lunars and two solars. Last month’s very shallow partial lunar eclipse set us up for the annular that occurs this week. In fact, the theoretical mid-point for the first of two eclipse seasons for 2013 occurs on May 7th at 7:00 UT/ 3:00 EDT when the longitude of the Sun equals the descending node where the Moon’s path crosses the ecliptic. This further sets us up for the third and weakest eclipse of the year, a grazing penumbral on May 25th.

Animation of the path of this week's annular solar eclipse. (Credit: NASA/GSFC/A.T. Sinclair).
Animation of the path of this week’s annular solar eclipse. (Credit: NASA/GSFC/A.T. Sinclair).

An annular eclipse occurs when the Moon eclipses the Sun while near apogee and is hence visually too small to entirely cover the Sun.

The Moon reaches apogee on May 13th at 13:32 UT/9:32AM EDT at 405,826 kilometres from Earth, just 3 days and 13 hours past New.

Annulars are currently more common than total solar eclipses, occurring 33.2% of the time in our current 5,000 year epoch versus 26.7% for total solar eclipses. The remainders are hybrid and partial eclipses. Annulars will become even more common as our Moon recedes from us at a current rate of about 3.8 centimetres a year. In about 1.4 billion years, the final brief total solar eclipse as seen from the Earth will occur. Likewise, somewhere back about 900 million years ago, the very first annular eclipse as seen from the Earth occurred.

Solar viewing with a properly fitted glass white light filter over the aperture of a Schmidt-Cassegrain telescope. (Photo by Author).
Solar viewing with a properly fitted glass white light filter over the aperture of a Schmidt-Cassegrain telescope. (Photo by Author).

Safety is paramount while viewing an annular solar eclipse. As mentioned above, an annular eclipse throughout all phases is much brighter than you’d expect. Thus precautions to protect your eyes MUST be taken throughout ALL phases of the eclipse. Permanent eye damage can result from staring at the Sun without proper protection, and this can be near instantaneous when done through an unfiltered telescope!

We witnessed the 1994 annular eclipse from the shores of Lake Erie, and can tell you that 5% of the Sun is still extremely bright. You wouldn’t even know an annular eclipse was underway at midday unless you were looking for it. Use only filters approved for eclipse viewing that fit snugly over the FRONT of your optics. Throw those old eyepiece screw-on filters away, as they can heat up and crack!

Check filters before use and never leave a telescope aimed at the Sun unattended. Projecting the Sun is another option via a telescope or “Sun Gun,” but again, never leave such a rig unattended, and keep finderscopes covered at all times. Also, telescopes with folded optical paths such as Schmidt-Cassegrains can heat up to dangerous levels and should not be used for projecting the Sun.

The path of the May 9th/10th annular eclipse across Australia & the Pacific. (Map courtesy of Michael Zeiler at Eclipse Maps, click to enlarge).
The path of the May 9th/10th annular eclipse across Australia & the Pacific. (Map courtesy of Michael Zeiler at Eclipse Maps, click to enlarge).

This eclipse has a magnitude rating of 0.9544, meaning that 95.44% of the diameter of the Sun will be eclipsed at its maximum. Keep in mind, this leaves about 8.9% percent of the Sun, or about 1/11th of its visual area exposed. This translates to only a 2.5 magnitude drop in brightness. Thus, the brightness of the Sun will drop from magnitude -27 to -24.5, still well over 25,000 times brighter than the Full Moon!

Note that this one crosses the International dateline as well.

The action for this eclipse begins as the partial phases touch down over Western Australia at sunrise at 21:25 UT on May 9th (The morning of May 10th in Australia). The annulus makes its appearance at 22:30 UT over western Australia, with its 172 kilometre wide track racing to the northeast over Tennant Creek in the Northern Territories and crossing the Cape York peninsula as it crisscrosses the path of last November’s total solar eclipse just north of Cairns.

A closeup of the path of the annular eclipse across Australia, click to enlarge. (Courtesy of Miichael Zeiler at Eclipse Maps).
A closeup of the path of the annular eclipse across Australia, click to enlarge. (Courtesy of Miichael Zeiler at Eclipse Maps).

Note that the eclipse will be 80% partial near Alice Springs and Uluru (Ayers Rock), presenting an excellent photo op. Michael Zeiler at Eclipse Maps also points out that the area near the town of Newman in Western Australia will see an amazing sunrise annular eclipse. The path of the annular eclipse will then traverse the Coral Sea crossing over islands in eastern Papua New Guiana, the Solomon Islands and Kiribati before reaching greatest annularity with a duration of 6 minutes and 3 seconds at latitude 2° 13’ north and longitude 175° 28’ east. The path of annularity crosses over Bairiki Atoll and makes last landfall over Fanning Island north of Kiribati. Note that most of Australia, New Zealand, Indonesia and the Philippines will see partial phases of the eclipse. The islands of Hawaii across the dateline will also see a 40-50% partial eclipse on May 9th before the event ends in the eastern Pacific at 03:25:23 UT.

Weather prospects for the eclipse look to be best along the track through Australia with less than 20% chance of cloud cover then getting progressively worse as the eclipse path tracks northeastward out to sea. The Solomon Islands region can expect cloud cover in the 60% range, while in Hawaii prospects are about 70%. Eclipser maintains a site dedicated to weather prospects for upcoming eclipses.

Solar activity is currently moderate, with several sunspot groups currently turned Earthward making for a photogenic Sun on eclipse day;

Sunspot activity as of May 5th. (Photo by Author).
Sunspot activity as of May 5th. (Photo by Author).

This eclipse belongs to saros series 138 and is number 31 of 70. This saros started with a 2% partial solar eclipse on June 6th, 1472 and will end with a 12% partial on July 11th,2716 AD having produced 3 total, 1 hybrid, 16 partial and 50 annular eclipses.

Fans of this saros may remember the last annular in this series which crossed South America on April 29th, 1995.

A sequence of eclipse pictures taken from Huntington Beach, California on May 20th, 2012. (Credit: jimnista/Universe Today flickr gallery).
A sequence of eclipse pictures taken from Huntington Beach, California on May 20th, 2012. (Credit: jimnista/Universe Today flickr gallery).

Catching a rising annular eclipse can also make for a stunning photograph. To catch the eclipse and the foreground horizon in silhouette, a DSLR with a 400mm lens running at 1/500th of a second shutter speed or faster is a good combination. Remember, you’ll have to aim this via projection. DO NOT look through the camera at the Sun! Exposures slower than 1/200th of a second are also out of the question, as you can damage the camera sensor at slow exposures.

Another cool effect to watch for is the appearance of tiny little “crescent Suns” littering the ground as sunlight streams through gaps in the tree leaves. This occurs because the gaps act like tiny little pinhole cameras.  A spaghetti strainer is also a highly scientific apparatus that can be used to mimic this effect!

Several solar observing satellites, including Hinode and the European Space Agency’s Proba-2 are poised to catch multiple partial solar eclipses on May 9th and 10th. We ran simulations of these this weekend:

Finally, if you’re like 99.99% of humanity, you’ll be watching this eclipse online. Slooh will be broadcasting this eclipse live.

Also, the eclipse will be broadcast live via the Coca-Cola Space Science Center starting at 5PM ET.

Amateur astronomer Geoff Sims @beyond_beneath will be tweeting near real time images of the eclipse from the path of annularity. Colin Legg (@colinleggphoto) will also be observing the event. Also check out:

-Australian observer Gerard Lazarus’s live feed of the eclipse.

–3News in New Zealand and Sky News Australia for eclipse coverage.

Got an ad hoc eclipse broadcast planned? Let us know and we’ll include it!

The next and final solar eclipse for 2013 is a hybrid (annular along one section of the path and total along another) on November 3rd across the mid-Atlantic and central Africa. Another annular eclipse doesn’t occur until April 29th 2014, and the next total solar eclipse occurs on March 20th, 2015.

If you’re in the region be sure to catch this rare celestial event in person, or watch the action worldwide online!

 

Posted on by Elizabeth Howell

Star’s Dying Gasp May Signal Black Hole’s Birth

Where is the Nearest Black Hole
Artist concept of matter swirling around a black hole. (NASA/Dana Berry/SkyWorks Digital)

A distinctive flash of light emanating from a dying star may make it possible for astronomers to watch a black hole being born, according to new research.

This burst of light, which might last three to 10 days, could be visible in optical light and also in infrared, which shows the heat signature of cosmic objects. While not as bright as a supernova — an exploding star — this signal could occur somewhere in the sky as often as once a year, according to simulations performed at the California Institute of Technology.

“That flash is going to be very bright, and it gives us the best chance for actually observing that this event occurred,” stated Caltech postdoctoral scholar Tony Piro, who led the research that is published in Astrophysical Journal Letters. “This is what you really want to look for.”

A big star essentially turns into a black hole when it falls into itself due to its large mass. The collapse shoots out protons and electrons from the core, creating neutrons and temporarily turning the core into a neutron star (a really, really dense object). This process also makes up neutrinos, which are infinitesimal but also extremely fast, moving nearly as fast as light does and bleeding the star of energy.

Combining observations done with ESO's Very Large Telescope and NASA's Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. The black hole blows a huge bubble of hot gas, 1,000 light-years across or twice as large and tens of times more powerful than the other such microquasars. The stellar black hole belongs to a binary system as pictured in this artist's impression. Credit: ESO/L. Calçada
Combining observations done with ESO’s Very Large Telescope and NASA’s Chandra X-ray telescope, astronomers have uncovered the most powerful pair of jets ever seen from a stellar black hole. The black hole blows a huge bubble of hot gas, 1,000 light-years across or twice as large and tens of times more powerful than the other such microquasars. The stellar black hole belongs to a binary system as pictured in this artist’s impression. Credit: ESO/L. Calçada

A 1980 paper, CalTech stated, showed that “this rapid loss of mass means that the gravitational strength of the dying star’s core would abruptly drop.” Hydrogen-filled layers at the top of the star would then fall outward and create a shock wave moving at more than two million miles an hour.

More recently, astronomers at the University of California, Santa Cruz discovered that the shock wave’s friction against the gas would heat up the plasma and make it glow, potentially for as long as a year. But that would be very faint from Earth-borne telescopes.

This is where the new CalTech research comes in. The university is already involved in black hole research, including the Nuclear Spectroscopic Telescope Array (NuSTAR). You can check out a video about NuSTAR below.

Piro’s simulations focus on when shock waves hit the surface of the star. It’s this process that would produce a burst of light, perhaps 10 to 100 times brighter than the other glow that astronomers foresaw.

The next step will be trying to observe these events as soon as they happen. Caltech advertised several survey possibilities related to its research: the Palomar Transient Factory, the  intermediate Palomar Transient Factory that started work in February and the even more advanced Zwicky Transient Facility (ZTF) that  is expected to start up in 2015.

Of course, it’s quite possible that other telescopes on the ground or orbit could work to confirm this signal.

Source: California Institute of Technology

Posted on by David Dickinson

Into Oblivion: What If the Earth Had No Moon?

A shattered Luna as depicted in the summer blockbuster Oblivion. (Credit: Universal Pictures).

AVAST gentle reader: mild SPOILER(S) and graphic depictions of shattered satellites ahead!

We recently had a chance to catch Oblivion, the first summer blockbuster of the season. The flick delivers on the fast-paced Sci-Fi action as Tom Cruise saves the planet from an invasion of Tom Cruise clones.

But the movie does pose an interesting astronomical question: what if the Earth had no large moon? In the movie, aliens destroy the Earth’s moon, presumably to throw our planet into chaos. You’d think we’d already be outclassed by the very definition of a species that could accomplish such a feat, but there you go.

Would the elimination of the Moon throw our planet into immediate chaos as depicted in the film? What if we never had a large moon in the first place? And what has our nearest natural neighbor in space done for us lately, anyway?

Earth is unique among rocky or terrestrial planets in that it has a relatively large moon. The Moon ranks 5th in diameter to other solar system satellites. It is 27% the diameter of our planet, but only just a little over 1/80th in terms of mass.

Clearly, the Moon has played a role in the evolution of life on Earth, although how necessary it was isn’t entirely clear. Periodic flooding via tides would have provided an initial impetus to natural selection, driving life to colonize the land. Many creatures such as sea turtles take advantage of the Full Moon as a signal to nest and breed, although life is certainly resilient enough to find alternative methods.

The 2000 book Rare Earth by Peter Ward and Donald Brownlee cites the presence of a large moon as just one of the key ingredients necessary in the story of the evolution of life on Earth. A Moon-less Earth is also just one of the alternative astronomical scenarios cited by Arthur Upgreen in his 2005 book Many Skies.

Save our satellite: A possible target for an alien attack? (Photo by author).
Save our satellite: A possible target for an alien attack? (Photo by author).

Contrary to its depiction on film, the loss of the Moon wouldn’t throw the Earth into immediate chaos, though the long term changes could be catastrophic. For example, no study has ever conclusively linked the Moon to the effective prediction of terrestrial volcanism and earthquakes, though many have tried. (Yes, we know about the 2003 Taiwanese study, which found a VERY weak statistical signal).

All of that angular momentum in the Earth-Moon system would still have to go somewhere. Our Moon is slowly “braking” the rotation of the Earth to the tune of about 1 second roughly every 67,000 years. We also know via bouncing laser beams off of retro-reflectors left by Apollo astronauts that the Moon is receding from us by about 3.8 cm a year. The fragments of the Moon would still retain its angular momentum, even partially shattered state as depicted in the film.

The most familiar effect the Moon has on Earth is its influence on oceanic tides. With the loss of our Moon, the Sun would become the dominant factor in producing tides, albeit a much weaker one.

But the biggest role the Moon plays is in the stabilization of the Earth’s spin axis over long scale periods of time.

Milankovitch cycles play a long term role in fluctuations in climate on the Earth. This is the result of changes in the eccentricity, obliquity and precession of the Earth’s axis and orbit. For example, perihelion, or our closest point to the Sun, currently falls in January in the middle of the northern hemisphere winter in the current epoch. The tilt of the Earth’s axis is the biggest driver of the seasons, and this varies from 22.1° to 24.5° and back (this is known as the change in obliquity) over a span of 41,000 years. We’re currently at a value of 23.4° and decreasing.

But without a large moon to dampen the change in obliquity, much wider and unpredictable swings would occur. For example, the rotational axis of Mars has varied over a span of 13 to 40 degrees over the last 10 to 20 million years. This long-term stability is a prime benefit that we enjoy in having a large moon .

Perhaps some astronomers would even welcome an alien invasion fleet intent on destroying the Moon. Its light polluting influence makes most deep sky imagers pack it in and visit the family on the week surrounding the Full Moon.

But I have but two words in defense of saving our natural satellite: No eclipses.

The diamond ring effect as seen during a 2008 total solar eclipse. (Credit: NASA/Exploratorium).
The diamond ring effect as seen during a 2008 total solar eclipse. (Credit: NASA/Exploratorium).

We currently occupy an envious position in time and space where total solar and lunar eclipses can occur.  In fact, Earth is currently the only planet in our solar system from which you can see the Moon snugly fit in front of the Sun during a total lunar eclipse. It’s 1/400th the size of the Sun, which is also very close to 400 times as distant as the Moon. This situation is almost certainly a rarity in our galaxy; perhaps if alien invaders did show up, we could win ‘em over not by sending a nuclear-armed Tom Cruise after ‘em, but selling them on eclipse tours… Continue reading “Into Oblivion: What If the Earth Had No Moon?”

Posted on by Elizabeth Howell

Stonehenge Was An Ancient Burial Ground For the Rich: Study

Stonehenge. Credit: Wikimedia Commons

The site of Stonehenge — that mysterious collection of British rocks that could have served as a calendar using the stars — was also a graveyard for the elite, according to new research.

A British group led by the University College London looked at 63 bodies surrounding the historical site. They determined these people were part of a group of elite families that brought their relatives to Stonehenge for burial over more than 200 years, starting from 2,900 BC.

The bodies were buried long before the rocks visible today were erected, though.

“The first Stonehenge began its life as a huge graveyard,” stated UCL’s Parker Pearson, who led the study. “The original monument was a large circular enclosure built 500 years before the Stonehenge we know today, with the remains of many of the cremated bodies originally marked by the bluestones of Stonehenge. We have also discovered that the second Stonehenge was built 200 years earlier than thought, around 2500 BC.”

The findings were broadcast on Britain’s Channel 4 in March.

A separate study, that will be broadcast on BBC 4 Monday (April 29), shows that humans were in the area of Stonehenge about 3,000 years before it was constructed — making human occupancy about 5,000 years than previously thought.

According to media reports, a team from the United Kingdom’s Open University spotted evidence of human activity about a mile from Stonehenge, in nearby Amesbury.

Archaeologists found an extinct species of cow, called a wild auroch, on the site as well, supposing that it was some sort of migration route that attracted human hunters.

Source: University College London

Posted on by David Dickinson

Comet Lemmon, Now in STEREO

Animation of Comet 2012 F6 Lemmon as seen from NASA's STEREO ahead spacecraft. (Credit: NASA/GFSC; animation created by Robert Kaufman).

An icy interloper was in the sights of a NASA spacecraft this past weekend.

Comet 2012 F6 Lemmon passed through the field of view of NASA’s HI2A camera as seen from its solar observing STEREO Ahead spacecraft. As seen in the animation above put together by Robert Kaufman, Comet Lemmon is now displaying a fine ion and dust tail as it sweeps back out of the inner solar system on its 10,750 year plus orbit.

Comet Lemmon has been a dependable performer for southern hemisphere observers early in 2013. As we reported earlier this month for Universe Today, this comet is now becoming a binocular object low in the dawn sky for northern hemisphere astronomers.

Comet Lemmon passed perihelion at 0.73 astronomical units from the Sun on March 24th. It’s currently in the +4th to +5 magnitude range as it heads northward through the constellation Pisces.

NASA’s twin Solar TErrestrial RElations Observatory (STEREO) spacecraft often catch sungrazing comets as they observe the Sun. Known as STEREO A (Ahead) & STEREO B (Behind), these observatories are positioned in Earth leading and trailing orbits. This provides researchers with full 360 degree coverage of the Sun. Launched in 2006, STEREO also gives us a unique perspective to spy incoming sungrazing comets. Recently, STEREO also caught Comet 2011 L4 PanSTARRS and the Earth as the pair slid into view.

Another solar observing spacecraft, the European Space Agencies’ SOlar Heliospheric Observatory (SOHO) has been a prolific comet discoverer. Amateur comet sleuths often catch new Kreutz group sungrazers in the act. Thus far, SOHO has discovered over 2400 comets since its launch in 1995. SOHO won’t see PanSTARRS or Lemmon in its LASCO C3 camera but will catch a glimpse of Comet 2012 S1 ISON as it nears the Sun late this coming November.

Like SOHO and NASA’s Solar Dynamics Observatory, data from the twin STEREO spacecraft is available for daily perusal on their website. We first saw this past weekend’s animation of Comet Lemmon passing through STEREO’s field of view on the Yahoo STEREOHunters message board.

Here’s a cool but largely unrecognized fact about comets. As they move back out of the solar system, their dust tail streams out ahead of them, driven by the solar wind. I’ve even seen a few science fiction flicks get this wrong. We simply expect comets to always stream their tails out behind them!

Another observatory in our solar observing arsenal has also moved a little closer to operability recently. The Interface Region Imaging Spectrograph (IRIS) arrived at Vandenberg recently in preparation for launch this summer on June 26th. IRIS will be deployed from a Pegasus XL rocket carried aloft by an L-1011. NuSTAR was launched in a similar fashion in 2012. A Pegasus XL rocket will also launch the TESS exoplanet hunting satellite in 2017.

Keep an eye out for Comet Lemmon as it emerges from the dawn twilight in the days ahead. Also, be sure to post those pics to Universe Today’s Flickr community, and keep tabs on the sungrazing action provided to us by SOHO and STEREO!

 

Posted on by David Dickinson

A ‘Shallow’ Lunar Eclipse Coming on April 25

The very early partial phase of the 2010 December solstice total lunar eclipse. This week's shallow eclipse will appear similar at its maximum. (Photo by author)

Eclipse season is upon us this week with the first eclipse of 2013, a brief partial lunar eclipse.

The lunar eclipse on April 25, 2013 is a shallow one, meaning only a paltry 1.47% of the lunar limb will be immersed in the dark umbra or inner shadow of the Earth. Observers can expect to see only a dark diffuse edge of the inner shadow nick the the Moon as is grazes the umbra.

A partial lunar eclipse this shallow hasn’t occurred since May 3rd, 1958 (0.9%) and won’t be topped until September 28th, 2034 (1.4%). This is the second slightest partial lunar eclipse for this century.

Another term for this sort of alignment is known as a syzygy, a great triple-letter word score in Scrabble!

A video simulation of the eclipse:

The eclipse will be visible in its entirety from eastern Europe & Africa across the Middle East eastward to southeast Asia and western Australia. The eclipse will be visible at moonrise from South America to Western Europe and occurring at moonset for eastern Australia and the Far East. The partially eclipsed Moon will be directly overhead just off the northeastern coast of Madagascar. The eclipse will not be visible from North America.

Two eclipse seasons occur each year when the nodal points of the Moon’s orbit intersect the ecliptic while aligned with the position of the Sun and the Earth’s shadow. The Moon’s orbit is inclined 5.15° degrees with respect to the ecliptic, which traces out our own planet’s path around the Sun. If this intersection occurs near New or Full Moon, a solar or lunar eclipse occurs.

The visibility region of Thursday's partial lunar eclipse.
The visibility region of Thursday’s partial lunar eclipse (Credit: NASA/GSFC/F. Espenak).

If the Moon’s orbit was not inclined to our own, we’d get two eclipses per lunation, one solar and one lunar.

2013 has 5 eclipses, 3 lunar and 2 annular. The minimum number of eclipses that can occur in a calendar year is 4, and the maximum is 7, as will next occur in 2038.

The 3 lunar eclipses in 2013 are this week’s partial eclipse on April 25th and two faint penumbral eclipses, one on May 25th and another on October 18th. There is no total lunar eclipse in 2013. The last one occurred on December 10th 2011, and the next one won’t occur until April 15th 2014, favoring the Pacific Rim region.

This eclipse will also set us up for the first solar eclipse of 2013, an annular eclipse crossing NE Australia (in fact crossing the path of last year’s total eclipse near Cairns) and the south Pacific on May 10th. The only solar totality that will touch the surface of the Earth in 2013 is  the hybrid eclipse on November 3rd spanning Africa and the South Atlantic with a maximum totality of 1 minute & 40 seconds.

Contact times for the April 25 shallow eclipse:

P1-The Moon touches the penumbra-18:03:41 UT

U1-The Moon touches the umbra-19:54:04 UT

Mid-Eclipse-20:08:37.5 UT

U4 -The Moon quits the umbra-20:21:04 UT

P4-The Moon quits the penumbra- 22:11:23 UT

The length of the partial phase of the eclipse is exactly 27 minutes, and the length of the entire eclipse is 4 hours, 7 minutes and 42 seconds.

This particular eclipse is part of saros series 112 and is member 65 of 72.

This saros cycle began in 859 C.E. on May 20th and will end in 2139 on July 12th with a penumbral lunar eclipse. One famous member of this series was 52.  This eclipse was one of many used by Captain James Cook to fix his longitude at sea on December 4th 1778. Christopher Columbus also attempted this feat while voyaging to the New World. It’s a fun project that anyone can try!

I also remember watching the last eclipse in this series from South Korea on April 15th 1995, a slightly better partial of 11.14%.

An occultation of the bright star Spica occurs just 20 hours prior as seen from South Africa across the southern Atlantic. This the 5th in a series of 13 occultations of the star by the Moon in 2013.

Occultation of Spica
The visibility region for the April 25th occultation of Spica. (Created by the Author using Occult 4.1.0.2).

The +2.8th magnitude star Zubenelgenubi (Alpha Librae) is occulted by the waning gibbous Moon just 15 hours after the eclipse for Australia and the South Pacific.

Another occultation of a bright star with potential this week is +4.7th magnitude Chi Virginis across North America on the morning of Wednesday, April 24th  centered on 4:24 UT.

Chi Virginis occultation
Visibility region for the occultation of Chi Virginis on April 24th. (Created by the author using Occult 4.1.0.2 software).

Also keep an eye out for +0.1 magnitude Saturn near the Full Moon. Saturn reaches opposition this weekend for 2013 on April 28th

Full Moon occurs near mid-eclipse at 20:00 UT/16:00 EDT on April 25th. Colloquial names for the April Full Moon are the Pink, Fish, Sprouting Grass, Egg, Seed, & Waking Moon.

Sure, the penumbral phases of an eclipse are subtle and may not be noticeable to the naked eye… but it is possible to see the difference photographically.  Simply take a photo of the Moon before it enters the Earth’s penumbra, then take one during the penumbral phase and then another one after.  Be sure to keep the ISO/f-stop and shutter speed exactly the same throughout. Also, this project only works if the eclipsed Moon is high in the sky throughout the exposures, as the thick air low to the horizon will discolor the Moon as well. Compare the shots; do you see a difference?

A penumbral eclipse would offer a good proof of concept test for hunting for transiting exoplanets as well, although to our knowledge, no one has ever attempted this.

Finally, calling out to all Universe Today readers in Madagascar. YOU may just be able to catch a transit  of the International Space Station in front of the Moon just as the ragged edge of the umbra becomes apparent on the limb of the Moon. Check CALSky a day or so prior to the eclipse for a refined path… it would be an unforgettable pic!

The position of the ISS on April 25th at 19:48UT, just minutes before the partial pahse of the eclipse begins. (Credit: Orbitron).
The position of the ISS on April 25th at 19:48UT, just minutes before the partial phase of the eclipse begins. (Credit: Orbitron).

And if any ambitious observer is planning to live stream the eclipse, let us know and we’ll add your embed to this post. We do not expect an avalanche of web broadcasts, but hey, we’d definitely honor the effort!  Slooh is usually a pretty dependable site for live eclipse broadcasts, and as of this writing seems to have broadcast scheduled in the cue.

Happy eclipse-spotting!

Posted on by Tammy Plotner

Bright Blazar’s Emission Defies Explanations

Artist's concept of the Hubble Space Telescope viewing ultraviolet light from the jet of the active galactic nucleus of PKS 1424+240. Clouds of hydrogen gas along the line of sight absorb the light at known frequencies, allowing the redshift and distance of each cloud to be determined. The most distant gas cloud determines the minimum distance to PKS 1424+240. Data from the Fermi Gamma-ray Space Telescope, shown on the horizon at the left, were also used for this study. (Image composition by Nina McCurdy, component images courtesy of NASA)

When it comes to sheer wattage, blazars definitely rule. As the brightest of active galactic nuclei, these sources of extreme high-energy gamma rays are usually associated with relativistic jets of material spewing into space and enabled by matter falling into a host galaxy’s black hole. The further away they are, the dimmer they should be, right? Not necessarily. According to new observations of blazar PKS 1424+240, the emission spectrum might hold a new twist… one that can’t be readily explained.

David Williams, adjunct professor of physics at UC Santa Cruz, said the findings may indicate something new about the emission mechanisms of blazars, the extragalactic background light, or the propagation of gamma-ray photons over long distances. “There may be something going on in the emission mechanisms of the blazar that we don’t understand,” Williams said. “There are more exotic explanations as well, but it may be premature to speculate at this point.”

The Fermi Gamma-ray Space Telescope was the first instrument to detect gamma rays from PKS 1424+240, and the observation was then seconded by VERITAS (Very Energetic Radiation Imaging Telescope Array System) – a terrestrially based tool designed to be sensitive to gamma-rays in the very high-energy (VHE) band. However, these weren’t the only science gadgets in action. To help determine the redshift of the blazar, researchers also employed the Hubble Space Telescope’s Cosmic Origins Spectrograph.

To help understand what they were seeing, the team then set a lower limit for the blazar’s redshift, taking it to a distance of at least 7.4 billion light-years. If their guess is correct, such a huge distance would mean that the majority of the gamma rays should have been absorbed by the extragalactic background light, but again the answers didn’t add up. For that amount of absorption, the blazar itself would be creating a very unexpected emission spectrum.

“We’re seeing an extraordinarily bright source which does not display the characteristic emission expected from a very high-energy blazar,” said Amy Furniss, a graduate student at the Santa Cruz Institute for Particle Physics (SCIPP) at UCSC and first author of a paper describing the new findings.

Bright? You bet. In this circumstance it has to over-ride the ever-present extragalactic background light (EBL). The whole Universe is filled with this “stellar light pollution”. We know it’s there – produced by countless stars and galaxies – but it’s just hard to measure. What we do know is that when a high-energy gamma ray photo meets with a low-energy EBL photon, they essentially cancel each other out. It stands to reason that the further a gamma ray has to travel, the more likely it is to encounter the EBL, putting a limit on the distance to which we can detect high-energy gamma ray sources. By lowering the limit, the new model was then used to ” calculate the expected absorption of very high-energy gamma rays from PKS 1424+240″. This should have allowed Furniss’ team to gather an intrinsic gamma-ray emission spectrum for the most distant blazar yet captured – but all it did was confuse the issue. It just doesn’t coincide with expected emissions using current models.

“We’re finding very high-energy gamma-ray sources at greater distances than we thought we might, and in doing so we’re finding some things we don’t entirely understand,” Williams said. “Having a source at this distance will allow us to better understand how much background absorption there is and test the cosmological models that predict the extragalactic background light.”

Original Story Source: University of California Santa Cruz News Release. For further reading: The Firm Redshift Lower Limit of the Most Distant TeV-Detected Blazar PKS 1424+240.

Posted on by David Dickinson

Mysterious Moon Flashes: Could the Transient Lunar Phenomena be Linked to the Solar Cycle?

The Moon, our nearest natural satellite. (Photo by author).

A key mystery in observational lunar astronomy may be at least partially resolved.

An interesting study appeared recently in the British Astronomical Association’s (BAA) March 2013 edition of their Lunar Section Circular. The study is one of the most comprehensive looks at possible connections between Transient Lunar Phenomena and the Solar Cycle.

Collection of TLP reports analyzed by Barbara Middlehurst & Sir Patrick Moore. The red dots indicate reddish events, the yellow one other colored events. (Wikimedia Commons image in the Public Domain).
Collection of TLP reports analyzed by Barbara Middlehurst & Sir Patrick Moore. The red dots indicate reddish events. The yellow ones represent other colored events. (Wikimedia Commons image in the Public Domain).

Transient Lunar Phenomena (or TLPs) are observations collected over the years of flashes or glows on the Moon. Since these phenomena often rely on a report made by a solitary observer, they have been very sparsely studied.

The term itself was coined by Sir Patrick Moore in 1968. One of the very earliest reports of a TLP event was the flash seen on the dark limb of the waxing crescent Moon by Canterbury monks in 1178.

Other reports, such as a daylight “star near of the daytime crescent Moon” seen by the residents of Saint-Denis, France on January 13, 1589 was almost certainly a close conjunction of the planet Venus. Bright planets such as Venus can be easily seen next to the Moon in the daytime.

A daytime Moon and Venus as seen from France on January 13th, 1589. (Created by the author in Starry Night).
A daytime Moon and Venus as seen from France on January 13th, 1589. (Created by the author in Starry Night).

A stunning illusion also occurs when the Moon occults, or passes in front of a bright star or planet. In fact, there’s a name for this psychological phenomenon of a bright star seeming to “hang” between the horns of the Moon just prior to an occultation, known as the Coleridge Effect. This takes its name from a line in Coleridge’s Rime of the Ancient Mariner;

“Till clomb above the eastern bar, the horned Moon with one bright star,

Within nether tip.”

Okay, we’ve never seen the “horned Moon clomb,” either. But this does describe a real illusion often seen during an occultation. The mind thinks that gap between the horns of the Moon should be transparent, and the lingering planet or star seems to cross that space on the dark limb, if only for a second. Incidentally, South American residents will get to check this out during the next occultation of Venus this year on September 8th.

So, what does this have to do with the 11-year solar cycle? Well, when you strip away many of the dubious observations of TLPs over the years, a core of well- documented events described by seasoned observers remains. Anyone who has sketched such a complex object as the Moon realizes that fine detail becomes apparent on scrutiny that may be missed in a casual glance. But one persistent assertion that has gone around the astronomical community for years is that an increase in the number of TLP events is linked to the peak of the solar cycle.

This was first suggested in 1945 by H. Percy Wilkins. A later study by Barbara Middlehurst in 1966 disproved the idea, citing no statistical correlation between sunspot activity and TLPs.

Of course, pundits have tried unsuccessfully to link the solar cycle to just about everything, from earthquakes to human activity to booms and busts of the stock market. Most flashes on the dark limb of the Moon are suspected to be meteorite impacts. In fact, the advent of high-speed photography has been able to reveal evidence for lunar strikes during intense meteor showers such as the Leonids and Geminids.

Flash of a Leonid impact captured on the limb of the Moon in 2006. Click image to see animation. (Credit: NASA Meteoroid Environment Office).
Flash of a Leonid impact captured on the limb of the Moon in 2006. Click image to see animation. (Credit: NASA Meteoroid Environment Office).

What’s at little less clear are the source of luminous “hazes” or “glows” noted by observers. Keep in mind; we’re talking subtle effects noted after meticulous study. NASA even commissioned a study of TLPs named Project Moon-Blink during the early Apollo program. About a third of TLP events have been observed near the bright crater Aristarchus. Researchers even managed to get Neil Armstrong to make an observation of the crater during a pass on Apollo 11. He noted that “there’s an area that is considerably more illuminated than the surrounding area. It seems to have a slight amount of fluorescence.”

Aristarchus crater (arrowed) near Full Moon. Note how bright it is compared to the surrounding terrain. (Photo by Author).
A crater with a relatively high albedo (Proclus, arrowed) near Full Moon. Note how bright it is compared to the surrounding terrain. (Photo by Author).

But what’s interesting in the recent BAA study conducted by Jill Scambler is the amount of data that was available. The study was a comprehensive analysis of TLPs noted by the BAA, the Association of Lunar and Planetary Observers (ALPO) and NASA from 1700 to 2010. Observations were weighted from 1 to 5, with 1 for reports from inexperienced observers to 5 for definitive and unambiguous TLP events.

The periodogram analysis comparing the frequency of TLPs with the sunspot cycle utilized a tool available from NASA’s Exoplanet Database to evaluate the data. If there was any mechanism whereby TLPs were being generated by solar activity, it had been suggested previously by Wilkins that perhaps out-gassing was being caused be solar irradiation or lunar dust was becoming electrostatically charged and suspended.

In fact, Surveyor 7 witnessed such a phenomenon during lunar twilight. To date, no human has witnessed a sunrise or sunset from the surface of the Moon, although astronauts witnessed several from lunar orbit.

"Horizon glow" as imaged from the lunar surface during twilight. (Credit: NASA).
“Horizon glow” as imaged from the lunar surface during twilight. (Credit: NASA).

The final conclusion of the BAA study cites that “Although there are theories that might infer that TLP would be more frequent during solar activity, from a sunspot cycle perspective there is no evidence to support this.”

The report provides an interesting perspective on the topic, especially with solar cycle 24 peaking over the next year. It also seems that reports of TLPs have declined in past decades. One of the most famous examples was the flash imaged on the Moon (thought to be a Leonid) by Leon Stuart in 1953. But in the modern era of astrophotography with the Moon under nearly continuous scrutiny, where are all the images of TLPs?

Granted, a core number (2%) of events suggest evidence of real activity on a Moon that we most often think of as geologically dead. As for the spurious sightings, it helps to recall the number of “sightings” in the 19th century of Vulcan transiting the face of the Sun. Where is Vulcan today, with the Sun being monitored around the clock?

We’re not immune to this sort of “echo effect” in the modern world of astronomy, either. For example, whenever an impact scar or flash is noted on Jupiter, as occurred in 2009 and 2012, other sightings are “seen” throughout the solar system. A similar psychological phenomenon occurred when Comet Holmes brightened in 2007. For a time, reports flying around the Internet suggested many comets where suddenly increasing in brightness!

It also interesting to note that many features such as Aristarchus and Ina Caldera also have a high brightness or albedo. Although the Full Moon seems pearly white, the albedo of the Moon is actually quite low at (13%), about that of worn asphalt. Bright ejecta and rays tend to stand out, especially approaching a Full Moon, such as occurs on May 25th.

You can even enhance the saturation of those lunar pics to bring out subtle color and reveal that the Moon isn’t as monochromatic as it appears to the naked eye;

A false-colored gibbous Moon enhanced to bright out subtle color. (Photo by author).
A false-colored gibbous Moon enhanced to bring out subtle color. (Photo by author).

Kudos to the team at the BAA for casting a critical scientific eye on a little studied phenomenon. Perhaps missions such as the Lunar Atmosphere and Dust Environment Explorer (LADEE) departing for the Moon this summer will shed more light on the curious nature of Transient Lunar Phenomena.

-The study can be read in the March 2013 edition of the British Astronomical Association’s Lunar Section Circular available as a free pdf.

Posted on by Tammy Plotner

Looking Into The Green Eye Of Planetary Nebula IC 1295

This intriguing picture from ESO’s Very Large Telescope shows the glowing green planetary nebula IC 1295 surrounding a dim and dying star. It is located about 3300 light-years away in the constellation of Scutum (The Shield). This is the most detailed picture of this object ever taken. Credit: ESO

Located on Cerro Paranal in the Atacama Desert of northern Chile, the ESO’s Very Large Telescope was busy using the FORS instrument (FOcal Reducer Spectrograph) to achieve one of the most detailed observations ever taken off a lonely, green planetary nebula – IC 1295. Exposures taken through three different filters which enhanced blue light, visible green light, and red light were melded together to make this 3300 light year distant object come alive.

Located in the constellation of Scutum, this jewel in the “Shield” is a miniscule star that’s at the end of its life. Much like our Sun will eventually become, this white dwarf star is softly shedding its outer layers, like an unfolding flower in space. It will continue this process for a few tens of thousands of years, before it ends, but until then IC 1295 will remain something of an enigma.

“The range of shapes observed up to today has been reproduced by many theoretical works using arguments such as density enhancements, magnetic fields, and binary central systems. Despite this, no complete agreement between models and properties of a given morphological group has been achieved. One of the main reasons for this is selection criteria and completeness of studied samples.” say researchers at Georgia State University. “The samples are usually limited by available images in few bands such as Ha, [NII] and [OIII]. Of course they are also limited by distance, since the further away the object is, the harder it is to resolve its structure. Even with the modern telescopes, obtaining a truly complete sample is far from being achieved.”

Why is this common deep space object like IC 1295 such a mystery? Blame it on its structure. It is comprised of multiple shells.- gaseous layers which once were the star’s atmosphere. As the star aged, its core became unstable and it erupted in unexpected releases of energy – like expansive blisters breaking open. These waves of gas are then illuminated by the ancient star’s ultraviolet radiation, causing it to glow. Each chemical acts as a pigment, resulting in different colors. In the case of IC 1295, the verdant shades are the product of ionised oxygen.

Loading player…

This video sequence starts with a broad panorama of the Milky Way and closes in on the small constellation of Scutum (The Shield), home to many star clusters. The final detailed view shows the strange green planetary nebula IC 1295 in a new image from ESO’s Very Large Telescope. This faint object lies close to the brighter globular star cluster NGC 6712. Credit: ESO/Nick Risinger (skysurvey.org)/Chuck Kimball. Music: movetwo

However, green isn’t the only color you see here. At the heart of this planetary nebula beats a bright, blue-white stellar core. Over the course of billions of years, it will gently cool – becoming a very faint, white dwarf. It’s just all part of the process. Stars similar to the Sun, and up to eight times as large, are all theorized to form planetary nebulae as they extinguish. How long does a planetary nebula last? According to astronomers, it’s a process that could be around 8 to 10 thousand years.

“Athough planetary nebulae (PNe) have been discovered for over 200 years, it was not until 30 years ago that we arrived at a basic understanding of their origin and evolution.” says Sun Kwok of the Institute of Astronomy and Astrophysics. “Even today, with observations covering the entire electromagnetic spectrum from radio to X-ray, there are still many unanswered questions on their structure and morphology.”

Original Story Source: ESO Photo Release.

Posted on by Nancy Atkinson

Join in an Online Messier Marathon

Online Messier Marathon with the Virtual Telescope Project.

Have you ever done a Messier Marathon? Want to try it online from the comfort of your own home? Astrophysicist Gianluca Masi will host a webcast today (April 9, 2013) at 18:00 UTC (2 pm EDT) (update: this webcast has been postponed due to clouds. We’ll post the new date and time when it becomes available). You can join in at this link, and explore the many treasures of the famous Messier Catalog. Masi said they will try to see as many of 110 objects in the Messier Catalog as possible in a single viewing session. This is what is called a Messier Marathon!

This is the fifth time the Virutal Telescope Project has attempted this, and they’ve had great success previously. Masi is doing the Marathon their robotic telescopes, and will provide real time images and live comments, along with answering your questions and “sharing your passion and excitement with friends from all around the world.”

For more information on how to join in see the Virtual Telescope Project’s website. For more info on a Messier Marathon and how to do one, see our excellent recent post by David Dickinson.

Here’s some examples of what you will be seeing today during the webcast: